netdevice: Fix promiscuity and allmulti overflow

Max of promiscuity and allmulti plus positive @inc can cause overflow.
Fox example: when allmulti=0xFFFFFFFF, any caller give dev_set_allmulti() a
positive @inc will cause allmulti be off.
This is not what we want, though it's rare case.
The fix is that only negative @inc will cause allmulti or promiscuity be off
and when any caller makes the counters touch the roof, we return error.

Change of v2:
Change void function dev_set_promiscuity/allmulti to return int.
So callers can get the overflow error.
Caller's fix will be done later.

Change of v3:
1. Since we return error to caller, we don't need to print KERN_ERROR,
KERN_WARNING is enough.
2. In dev_set_promiscuity(), if __dev_set_promiscuity() failed, we
return at once.

Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4bf613cd9e2d..45dce2b58d4c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1476,8 +1476,8 @@ extern int 		__dev_addr_delete(struct dev_addr_list **list, int *count, void *ad
 extern int              __dev_addr_add(struct dev_addr_list **list, int *count, void *addr, int alen, int newonly);
 extern int              __dev_addr_sync(struct dev_addr_list **to, int *to_count, struct dev_addr_list **from, int *from_count);
 extern void             __dev_addr_unsync(struct dev_addr_list **to, int *to_count, struct dev_addr_list **from, int *from_count);
-extern void             dev_set_promiscuity(struct net_device *dev, int inc);
-extern void             dev_set_allmulti(struct net_device *dev, int inc);
+extern int              dev_set_promiscuity(struct net_device *dev, int inc);
+extern int              dev_set_allmulti(struct net_device *dev, int inc);
 extern void             netdev_state_change(struct net_device *dev);
 extern void             netdev_bonding_change(struct net_device *dev);
 extern void             netdev_features_change(struct net_device *dev);